Field of the Invention
The present invention relates, in general, to a variable geometry turbocharger (VGT), which is a family of turbochargers used to boost engines using exhaust gas and, more particularly, to a sealing-coupled apparatus of a turbocharger, which is configured to prevent damage or breakage of a turbine vane due to a thermal deformation of a turbine housing.
Description of Related Art
A turbocharger, which is a turbine-driven forced induction device used to increase the fuel economy in addition to being used to increase an engine's efficiency, power and torque, is installed in automobiles. In the related art, a wastegate valve turbocharger (WGT) is also used. The WGT is configured such that, when a boost pressure in the turbocharger is too high, the WGT can mechanically reduce the boost pressure by opening a wastegate valve and bypassing a part of exhaust gas via the opened wastegate valve. The WGT is configured to provide a predetermined pressure ratio at a predetermined engine rpm and a predetermined engine load, so the WGT can sufficiently boost the engine at high speeds, but may create turbo lag at low speeds, leading to a reduction in the performance of the WGT.
In recent years, because Euro-4 legislation became effective on passenger diesel engines, restrictions have been imposed on exhaust gas from passenger diesel engines. Therefore, installation of exhaust gas recirculation valves (EGR valves) and variable geometry turbochargers (VGT) in passenger diesel engines is now required. In comparison with general turbochargers, it is noted that the VGT can increase engine's efficiency, power, torque and the fuel economy to some degree.
In variable geometry turbochargers (VGT), to avoid undesired fixing of a turbine vane due to a thermal deformation of a turbine housing, an insert functioning as a vane cover is installed. Here, the insert is spaced apart from the turbine housing at a predetermined interval in an axial direction. A conventional insert used in the VGT is provided with a sealing structure on a tubular member set in the turbine housing. When the VGT is repeatedly operated under high temperature conditions, the insert may be deformed by a reaction force of the sealing structure caused by a thermal deformation of the turbine housing. When the insert is deformed as described above, the interval between the inner surface of the insert and the turbine vane is reduced, so the turbine vane may be damaged or broken due to rotational vibrations thereof.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.